[S390] dynamic page tables.

Add support for different number of page table levels dependent
on the highest address used for a process. This will cause a 31 bit
process to use a two level page table instead of the four level page
table that is the default after the pud has been introduced. Likewise
a normal 64 bit process will use three levels instead of four. Only
if a process runs out of the 4 tera bytes which can be addressed with
a three level page table the fourth level is dynamically added. Then
the process can use up to 8 peta byte.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 40 insertions, 0 deletions

diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index 2456b52ed06..ed13d429a48 100644
--- a/arch/s390/mm/fault.c
+++ b/arch/s390/mm/fault.c
@@ -32,6 +32,7 @@
 #include <asm/system.h>
 #include <asm/pgtable.h>
 #include <asm/s390_ext.h>
+#include <asm/mmu_context.h>
 
 #ifndef CONFIG_64BIT
 #define __FAIL_ADDR_MASK 0x7ffff000
@@ -444,6 +445,45 @@ void __kprobes do_dat_exception(struct pt_regs *regs, unsigned long error_code)
         do_exception(regs, error_code & 0xff, 0);
 }
 
+#ifdef CONFIG_64BIT
+void __kprobes do_asce_exception(struct pt_regs *regs, unsigned long error_code)
+{
+        struct mm_struct *mm;
+        struct vm_area_struct *vma;
+        unsigned long address;
+        int space;
+
+        mm = current->mm;
+        address = S390_lowcore.trans_exc_code & __FAIL_ADDR_MASK;
+        space = check_space(current);
+
+        if (unlikely(space == 0 || in_atomic() || !mm))
+                goto no_context;
+
+        local_irq_enable();
+
+        down_read(&mm->mmap_sem);
+        vma = find_vma(mm, address);
+        up_read(&mm->mmap_sem);
+
+        if (vma) {
+                update_mm(mm, current);
+                return;
+        }
+
+        /* User mode accesses just cause a SIGSEGV */
+        if (regs->psw.mask & PSW_MASK_PSTATE) {
+                current->thread.prot_addr = address;
+                current->thread.trap_no = error_code;
+                do_sigsegv(regs, error_code, SEGV_MAPERR, address);
+                return;
+        }
+
+no_context:
+        do_no_context(regs, error_code, address);
+}
+#endif
+
 #ifdef CONFIG_PFAULT 
 /*
  * 'pfault' pseudo page faults routines.